Blizzard Watch 5, NWS Anchorage, AK

648 
WWAK42 PAFC 131320
WSWALU

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE ANCHORAGE AK
420 AM AKST MON FEB 13 2017

AKZ155-131430-
/O.CAN.PAFC.WW.Y.0014.000000T0000Z-170213T1800Z/
KUSKOKWIM DELTA-
INCLUDING THE CITIES OF...BETHEL...HOOPER BAY...NUNIVAK ISLAND
420 AM AKST MON FEB 13 2017

...WINTER WEATHER ADVISORY IS CANCELLED...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS CANCELLED THE
WINTER WEATHER ADVISORY. 

WHILE COLD NORTH WINDS CONTINUE THEY HAVE NOT BEEN SUFFICIENT TO
PICK UP MUCH BLOWING SNOW. LIGHT SNOW TODAY COMBINED WITH THE
WINDS MAY STILL REDUCE VISIBILITIES AT TIMES BUT THEY ARE NOT
EXPECTED TO FALL TO ADVISORY LEVELS. WIND CHILLS CURRENTLY AROUND
MINUS 35 F WILL GRADUALLY WARM THROUGH THE MORNING.

$$

AKZ195-140300-
/O.UPG.PAFC.BZ.A.0005.170214T0600Z-170215T0600Z/
/O.NEW.PAFC.BZ.W.0004.170214T0600Z-170215T0600Z/
PRIBILOF ISLANDS-
INCLUDING THE CITY OF...SAINT PAUL
420 AM AKST MON FEB 13 2017

...BLIZZARD WARNING IN EFFECT FROM 9 PM THIS EVENING TO 9 PM AKST
TUESDAY...

THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS ISSUED A BLIZZARD
WARNING...WHICH IS IN EFFECT FROM 9 PM THIS EVENING TO 9 PM AKST
TUESDAY. THE BLIZZARD WATCH IS NO LONGER IN EFFECT. 

* LOCATION...THE PRIBILOF ISLANDS.

* SNOW...4 TO 6 INCHES.

* VISIBILITY...REDUCED TO ONE QUARTER MILE OR LESS AT TIMES.

* WIND...NORTH WINDS 35 TO 45 MPH.

* TIMING...WINDS WILL RAMP UP THIS EVENING WITH THE STRONGEST
  WINDS OCCURRING IN THE EARLY MORNING HOURS OF TUESDAY. WINDS
  WILL TAPER DOWN STARTING TUESDAY NIGHT. SNOWFALL INTENSITY WILL
  BEGIN INCREASING LATE THIS EVENING OR EARLY TUESDAY MORNING WITH
  ANOTHER PERIOD OF HEAVIER SNOW POSSIBLE MIDDAY TUESDAY.

* IMPACTS...SNOWFALL COMBINED WITH STRONG WINDS AND BLOWING SNOW
  WILL PRODUCE WHITE-OUT CONDITIONS AT TIMES. DRIVING MAY BECOME
  VERY DIFFICULT.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A BLIZZARD WARNING MEANS SEVERE WINTER WEATHER CONDITIONS ARE
EXPECTED OR OCCURRING. FALLING AND BLOWING SNOW WITH STRONG WINDS
AND POOR VISIBILITIES ARE LIKELY. THIS WILL LEAD TO WHITE-OUT
CONDITIONS, MAKING TRAVEL VERY DIFFICULT. ALL TRAVEL AND OUTDOOR
ACTIVITY IS STRONGLY DISCOURAGED.

&&

$$

AKZ161-140300-
/O.EXT.PAFC.WW.Y.0014.000000T0000Z-170214T0900Z/
BRISTOL BAY-
INCLUDING THE CITIES OF...KING SALMON...DILLINGHAM...NAKNEK...
PILOT POINT
420 AM AKST MON FEB 13 2017

...WINTER WEATHER ADVISORY FOR SNOW AND BLOWING SNOW IN EFFECT
UNTIL MIDNIGHT AKST TONIGHT NORTH AND WEST OF KING SALMON...

* LOCATION...NORTH AND WEST OF KING SALMON.

* SNOW...6 TO 10 INCHES.

* VISIBILITY...REDUCED TO ONE HALF MILE OR LESS AT TIMES.

* WIND...NORTH WINDS 15 TO 25 MPH WITH GUSTS TO 35 MPH.

* TIMING...SNOW AND BLOWING SNOW WILL CONTINUE THROUGH THIS
  EVENING BEFORE DIMINISHING AFTER MIDNIGHT. 

* IMPACTS...TRAVEL MAY BE DIFFICULT. VISIBILITIES WILL BE 
  LIMITED IN FALLING AND BLOWING SNOW. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER WEATHER ADVISORY FOR SNOW AND BLOWING SNOW MEANS THAT
VISIBILITIES WILL BE LIMITED DUE TO A COMBINATION OF FALLING AND
BLOWING SNOW. USE CAUTION WHEN TRAVELING... ESPECIALLY IN OPEN
AREAS.

&&

$$

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
600 AM AKST Sun Feb 12 2017

.ANALYSIS AND UPPER LEVELS...

An arctic airmass is in place across virtually all of southern
Alaska this morning with temperatures below zero around most of
the Cook Inlet area, the Copper River Basin, as well as Southwest
Alaska. Change is on the horizon, though, as the longwave pattern
is in the process of amplifying dramatically. Ridging is building
over the west coast of North America and will eventually build
toward the panhandle, which will switch winds to southerly across
Southcentral Alaska and bring in warm air and copious moisture.

Out west, cold northerly flow and instability snow showers continue
over pretty much all of the Bering Sea. Satellite imagery reveals
the sea ice is growing quickly and surging southward.

&&

.MODEL DISCUSSION...

The models are slowly coming into better agreement on the approach
and evolution of the initial low pressure center coming up from
the south. The GFS had previously been a significant outlier
moving the energy toward the interior parts of the state rather
than recurving back into Bristol Bay, but the new GFS runs have
joined the consensus. As for the 2nd (Tuesday) and possibly 3rd
(Wednesday) reinforcing waves that move toward southcentral AK,
there is still considerable model spread. Not only are position
and timing of the features in question, but the associated
thermodynamics and extent of warm air as well as the role of
downsloping are all in the mix with higher than normal
uncertainty. All of this adds up to a forecast picture for the
first half of the week with even less confidence than normal, with
the potential for the forecast to go awry in a number of ways.
Overall the NAM was the preferred model for updates to the short
term forecast today.

&&

.AVIATION...
PANC...The day starts out clear (VFR) and cold, but midlevel
clouds will quickly build in by midday. By this evening some
flurries or light snow becomes possible, getting more likely by
midnight with the ceiling dropping to low-VFR but probably holding
there through Monday morning as deep cold air keeps the lowest
levels of the atmosphere somewhat dry. Variable winds this morning
will give way to a steady north wind by this afternoon, which
should also remain fairly constant through Monday morning.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 and 2)...

A big pattern change is on the way for Southcentral Alaska as the
upper level pattern is quickly changing. Previously, the jet
stream was located over the northern Pacific Ocean south of
Alaska. However, a series of upper level disturbances have helped
amplify the longwave pattern and in turn has dug out a deep
trough over the northern Pacific Ocean with the eastern part of
the upper level trough pointed straight at Southcentral Alaska.
This will allow a tap into very moist and very warm subtropical
air to develop and advect northward toward Alaska. In the meantime,
temperatures have dropped off significantly the past 24 to 36
hours in the wake of a very cold arctic trough that brought snow
showers to much of the region. Well below normal temperatures will
continue through the morning with many interior locations already
reporting temperatures that are well below zero inland with coastal
locations generally in the single digits to lower teens.

The period of dry and colder weather will be short lived as a
series of lows and fronts from the north Pacific quickly move
northward into the Gulf of Alaska. As this happens, a very warm
air mass will begin to erode the cold air mass that just situated
itself over Alaska just yesterday. Initially, it looks like heavy
snow will upslope along the eastern Kenai Peninsula and Prince
William Sound Area but by Monday afternoon, many locations along
the coast will begin transitioning to rain. Models have trended
further west with the low placement toward the west side of Kodiak
Island which will likely keep Anchorage downsloped through much of
the event although a significant warm-up is still expected. Some
snow showers, then possibly a short duration of freezing rain and
then finally intermittent light rain will be possible for Anchorage
on Monday which could really cause travel and commuting issues.

The Susitna Valley will likely continue to pull in colder
temperatures from the interior of Alaska and see some decent
snowfall. A Winter Weather Advisory has been issued for the
Susitna Valley Sunday night and Monday as blowing snow concerns
through Broad Pass are expected with moderate snowfall and winds
between 15 and 30 mph. In addition, snowfall between 4 to 8 inches
is expected west of the parks highway as moisture upslopes along
the terrain.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)...
Cold and dry offshore flow will be the main story for one more
day before the approaching North Pacific low initiates a change to
a warmer and snowier pattern for the beginning of the work week.
Snow will first spread into the Bristol Bay region late this
evening as a front moves into the region from the southeast. There
is a chance for several inches of snow to fall across some
portions of Bristol Bay by late Monday morning, potentially aided
by mid-level deformation on the northwest periphery of the
system. However, confidence in overall snowfall totals remains low
as there is still uncertainty over the placement and duration of
this feature. Additionally, blowing snow will become a possibility
as northerly winds increase ahead of the system and temperatures
remain well below freezing, with areas north and west of King
Salmon most likely to see blowing snow tonight into Monday
morning. Snow will then spread over the rest of the southwest
mainland during the day on Monday and persist into Tuesday as the
North Pacific system crosses the Alaska Peninsula. The system will
then merge with an upper level trough descending from the
northern interior, lingering near the Alaska Peninsula through
the middle of the week.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)...
The approaching North Pacific low will keep the most significant
weather impacts confined primarily to the Pacific coastal waters
of the Akpen through Monday. Gale-force winds will be the main
impacts to the southeast Bering as the heaviest precipitation
remains east of Sand Point. Meanwhile, the rest of the Bering
region will remain in a much more benign northerly flow regime
characterized by scattered snow showers. Attention then turns to
the Pribilof Islands late Monday as the phasing of the upper
trough and the current North Pacific system acts to enhance snow
showers and northerly winds, leading to potential blowing snow
concerns Monday night.

&&

.LONG TERM FORECAST (Days 3 through 7)...
By Monday night the next deep low pressure center will be
rotating across the southern end of Kodiak Island while the
associated frontal system lifts north across the northern Gulf
Coast and into Southcentral Alaska. With this being the second
intrusion of warm, moist air inland and with more pronounced
downsloping southeasterly flow...expect rain to spread further
inland with the system. There is still significant uncertainty
regarding where in the Susitna Valley the rain/snow line will set
up but further south, above freezing temperatures look very likely
for the lower to mid elevations (below 1500 ft inland and 2500 to
3000 ft near the Gulf Coast).

Conditions also look favorable for a strong barrier jet to
develop Monday Night and Tuesday bringing at least strong Gales
to the northern Gulf coastal waters and extending into Prince
William Sound. These strong east to southeast winds will funnel
and accelerate through Portage Valley and Turnagain Arm as well as
along the ridges of the Kenai Peninsula and Chugach Mountains.
Models rapidly diverge Tuesday and Wednesday with regards to
timing and position of lows but agree on another strong frontal
wave or two lifting across the Gulf through midweek. Cooler
temperatures return with an upper level trough and southwesterly
flow Thursday and Friday, bringing the snow level back down to
sea level. Numerous lows and troughs rotating in from the western
Gulf will bring the potential for snow at times to Southcentral
from Thursday through the weekend.

For Southwest Alaska easterly waves rotating across the Alaska
and Aleutian ranges will be the primary concern through midweek as
an upper level low remains centered over the western Alaska
Peninsula with an accompanying deep pool of cold air. The initial frontal
wave crossing Southwest Alaska Monday night will bring a good
potential for snow, followed by several more Tuesday and
Wednesday. To the west of the upper level low, northerly flow will
continue with scattered to numerous snow showers continuing across
much of the Bering. An arctic upper level trough becomes
established over western Alaska Thursday and Friday bringing a
drying trend and a return to very cold temperatures.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC... Winter Weather Advisory- 145
MARINE...Gales 119 120 125 130 131 138 139 150 155 172 180 351
352.
Heavy Freezing Spray 127 130 139 141 155 165 170 179 185 412 414.

&&

SYNOPSIS AND MODEL DISCUSSION...AD
SOUTHCENTRAL ALASKA...EN
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...DS